Numerous hydrocarbon conversion processes are widely used to alter the structure or properties of hydrocarbon streams. Such processes include isomerization from straight chain paraffinic or olefinic hydrocarbons to more highly branched hydrocarbons, dehydrogenation for producing olefinic or aromatic compounds, reforming to produce aromatics and motor fuels, alkylation to produce commodity chemicals and motor fuels, transalkylation, and others.
Many such processes use catalysts to promote hydrocarbon conversion reactions. These catalysts tend to deactivate for a variety of reasons, including the deposition of coke upon the catalyst, and/or loss of catalytic metal promoters such as halogens. Consequently, these catalysts are typically reactivated in a process called regeneration. Regeneration can include, among other things, removing coke from the catalyst by burning (combustion), and replenishing catalytic promoters such as halogens on the catalyst, and drying the catalyst.
One of the problems during regeneration of halogen-containing catalysts is the loss of halogen from the catalyst. This happens when catalyst particles are contacted with gases that, while regenerating the catalyst particles, tend also to remove halogen from the catalyst particles. Therefore, processes have been developed for returning a halogen to catalyst particles undergoing regeneration. For example, U.S. Pat. No. 6,881,391 discloses a method for regenerating catalyst particles wherein chlorine-containing vent gas from a catalyst regenerator is sent to an adsorption/desorption system to recover the chlorine, and the recovered chlorine is passed back to the catalyst regenerator.
Water can build up in the circulating gas, and if using a catalyst sensitive to moisture, then moisture reduction becomes desirable.
Therefore, what is needed is an improved process for the regeneration of halogen-containing catalysts wherein excess moisture can be removed from the process streams of the catalyst regeneration system.